1. Field of the Invention
The invention relates to an electronic adapter and a method for controlling a bistable valve.
2. Description of the Background Art
Valves may be applied in medical technology, e.g. in dialysis machines and analyzers, and in ink jet printers or in a plurality of fields where aggressive or delicate media have to be controlled.
In most applications monostable valves are preferred over bistable ones. Monostable valves have only one stable switching state, i.e. they may be switched to an instable state, e.g. by applying a voltage to a solenoid and remain in the instable state as long as the voltage is maintained. As soon as the voltage falls below a certain level the valve drops back in its stable state. This allows for setting the valve to a defined state in case of a power failure. However, the monostable valve requires a remarkable amount of energy when being kept in its instable state. Besides the energy consumption this usually results in warming of the valve, its environment and above all warming of the medium to be controlled which may be particularly undesirable in some applications. The solenoid has to be dimensioned to cope with the permanent current feed and the resulting warming.
Bistable valves by contrast have two stable switching states. They only need a short current pulse to switch to the respective other switching state. Hence, they neither have remarkable power consumption nor do they heat the medium to be controlled. However, they do not have a default switching state in case of a power loss which keeps them from being applied in environments where this is critical. Furthermore, controlling the bistable valve is more complicated since pulses have to be generated and the polarity of the switch voltage has to be changed. Failure of the control signals, e.g. permanent current feeding of the bistable valve, which is dimensioned for pulse operation only, may result in overheating and destruction of the valve.
US 2008/0179553 A1 discloses a solenoid operated valve for controlling liquid or gaseous media, the valve comprising at least two media ports opened and closed by an armature and a solenoid with a yoke and a coil, wherein the armature consisting of a magnetisable material is movably arranged inside a valve body housing consisting of a non-magnetic material, wherein the media ports empty into the valve body housing, wherein the valve body housing is arranged between the yoke and an additional element for magnetically interacting with the armature.